Large quake seldom causes large volcano eruptions

History records showed it was not often that large earthquakes caused immediate large volcano eruptions, a geophysicist told Xinhua on Wednesday while talking about whether the recent massive quake in Japan could trigger volcano eruptions.

Video image taken from NHK shows the area which is affected by the quake in northeast Japan, March 11, 2011. An earthquake measuring 8.6 on the Richter scale jolted off the east coast of Japan's main Honshu island on Friday. [Xinhua]

Inevitably, the shaking and changes in the state of stress in the crust could cause some changes in some of active volcanoes closest to the March 11 quake zone in Japan, said Dr. Jian Lin, senior scientist and geophysicist at the Woods Hole Oceanographic Institution in the United States.

However, only if a particular volcano was already in a stage of magmatic inflation, a situation close to eruption, would the shaking make a major difference, he noted.

Lin is currently visiting the U.S. Geological Survey's earthquake research center in Menlo Park, California to study the March 11 Japan earthquake.

Compared with the cases that earthquake triggered volcano eruptions in the past, Lin said, most of active volcanoes in Japan are located somewhat farther away from the March 11 earthquake rupture zones. "The farther away, the less direct effect," he noted.

Therefore, "the most important thing is to closely monitor all the active volcanoes in Japan," he said.

There are only two well-documented cases of significant volcano eruptions that were apparently triggered by large earthquakes, he said.

On Nov. 29, 1975, the Kilauea Volcano in the Hawaiian Islands had a small and short-lived eruption immediately after a magnitude- 7.2 quake hit the Big Island of Hawaii near the volcano, which was probably the best scientifically documented case so far of a volcano eruption triggered by a large earthquake.

Records showed that the Kilauea Volvano was already in a stage of inflation before the quake. Meanwhile, the quake was right next to the volcano, which triggered the following eruption.

Another case is 1960 Chile earthquake-volcano pair, in which a magnitude-9.5 earthquake, the largest ever recorded by instruments, could have triggered the Puyehue-Cordon Caulle Volcanic Complex ( PCCVC) into a violent eruption within 38 hours. The CCVC had been inactive for 25 years before the quake.

Lin pointed out that like the Kilauea case, the earthquake rupture zone in the Chilean quake was again quite close to the volcanic group. However, little scientific monitoring data had been got for the PCCVC before its eruption as it is in a remote area in Chile.

In recent years, scientists have observed that large earthquakes from long distance could trigger swarms of small earthquakes in active hydrothermal systems of volcanic regions, he said, noting that "these small earthquake swarms like these are not the same as volcano eruption."

Lin added that the relationship between large volcano eruption and large earthquakes is still a poorly studied subject since scientific record is very short and many of large eruptions in the geological history were poorly documented.